The present invention relates generally to logistics and, more particularly, to a GPS based system for spreading ballast along railroad tracks for track maintenance.
Conventional railroads in the United States and elsewhere are typically formed by a compacted sub-grade, a bed of gravel ballast, wooden cross-ties positioned upon and within the ballast, and parallel steel rails secured to the ties. Variations of construction occur at road and bridge crossings and in other circumstances. The ballast beneath and between the ties stabilizes the positions of the ties, keeps the rails level, and provides some cushioning of the composite structure for loads imposed by rail traffic. Vibrations from the movement of tracked vehicles over the rails and weathering from wind, rain, ice, and freeze and thaw cycles can all contribute to dislodging of some of the ballast over time. Thus, in addition to other maintenance activities, it is necessary to replace ballast periodically to maintain the integrity and safety of railroads.
Conventionally, ballast is spread using specially configured ballast hopper cars which include a hopper structure holding a quantity of ballast, a ballast chute communicating with the hopper, and a motorized ballast discharge door in the chute. The door can be controlled to selectively open or close to control the discharge of ballast. In some designs, the discharge door can be controlled to open outboard toward the outside of the rails, to close, or to open inboard toward the inside between the rails. Typical ballast hopper cars have a front hopper and a rear hopper, and each hopper has two transversely spaced doors, one to the left and one to the right. Thus, each hopper door can be controlled to discharge ballast outside the rails on the left and/or the right or between the rails. A typical configuration of a ballast hopper car is described in more detail in U.S. Pat. No. 5,657,700, which is incorporated herein by reference.
In general, ballast spreading has been controlled manually in cooperation with spotters who walk alongside the moving ballast cars to open or close the ballast doors as necessary. A more recent ballast spreading control technique is by the use of a radio linked controller carried by an operator who walks alongside the moving ballast cars. Both conventional control methods are so slow as to disrupt normal traffic on the railroad section being maintained, thereby causing delays in deliveries and loss of income.
Copending application, Ser. No. 09/285,290, generally discloses methods for spreading railroad ballast with location control based on data received from the global positioning system or GPS. The GPS system, also referred to as NAVSTAR, is a xe2x80x9cconstellationxe2x80x9d of satellites traveling in orbits which distribute them around the earth, transmitting location and time signals. As originally designed, a GPS receiver, receiving signals from at least four satellites, was able to process the signals and triangulate position coordinates accurate to about ten to twenty meters. Current generations of commercially available GPS receivers, using differential GPS techniques, are able to achieve accuracies in the range of one to five meters. Such accuracy is adequate for depositing ballast where desired and inhibiting the deposit of ballast where it is not desired. Additional information regarding the development of GPS technologies can be obtained from U.S. Pat. Nos. 4,445,118 and U.S. Pat. No. 5,323,322 which are incorporated herein by reference. Development of the GPS system referred to herein was sponsored by the United States government. However, satellite based positioning systems developed or operated by other nations are also known.
Because railroad companies typically maintain hundreds or thousands of miles of track on a recurring schedule, the ballast replacement component of track maintenance alone can be a major undertaking in terms of equipment, materials, traffic control, labor, and management. Knowing the ballast capacity of the hoppers of a ballast car and the flow rate through the ballast doors, it would be possible to provide each ballast car with a GPS receiver, to program an individual on-car computer with a set of spread coordinates and ballast distribution parameters, and to control the flow of ballast in a spread zone in relation to measured or computed car speed. However, such an approach would be expensive in terms of GPS receivers and control computers and would be extremely laborious for a large project. Additionally, coordination and record keeping would be complicated by such a piecemeal approach.
The present invention provides methods and apparatus for controlled spreading of ballast on a railroad on a large scale basis using multiple ballast hopper cars spreading simultaneously, at times. The system of the present invention uses location coordinates provided by a differential GPS receiver to coordinate the opening of ballast doors to spread controlled quantities of ballast on sections where ballast is desired and to inhibit spreading ballast where not desired or not needed. The system allows the ballast train to spread ballast mostly at a high enough speed that normal traffic on the railroad on which it is operating is only minimally affected by its presence.
In practice of the present invention, a ballast train includes one or more locomotives, a control car, and a plurality of ballast hopper cars, such as fifty hopper cars. Each hopper car has two hoppers, left and right ballast chutes for each hopper, a ballast door for each chute, and a hydraulic actuator for each door. The actuator can be controlled to open its associated door to an inboard direction, between the rails, or to an outboard direction, outside of the rails. Each hopper can hold a known load of a particular type of ballast, and the average flow rate of a given type of ballast through a ballast door is also known. Each hopper car has car logic circuitry, referred to as a car control unit or CCU and also as a xe2x80x9cneuronxe2x80x9d, which controls operation of the hydraulic actuators and which monitors certain functions on the car.
The CCU""s communicate with a central control or head end controller (HEC) through a network including a bus referred at places herein as a xe2x80x9cwirelinexe2x80x9d. The bus extends from the HEC through the CCU of each car, interrupted by a set of a front and a rear communication relay in each CCU, which is controlled by the local CCU. The communication relays can be used to determine the orientation of each car by a procedure which will be detailed below. The HEC may be a general purpose type of computer, such as a laptop, and has a differential GPS receiver interfaced thereto to provide geographic coordinates. The GPS receiver includes a GPS antenna, the location of which forms a reference location or datum for the train. The relative location of each ballast door on each hopper car of the train will be determined in relation to the reference location. Ordinarily, the ballast train will use a plurality of virtually identical hopper cars with known distances between the ballast doors on a given car and between the ballast door of one car and the next adjacent car.
In order to control the spreading of ballast on a length of track, it is necessary to obtain the geographic coordinates of the track. This is most conveniently accomplished by a survey run on the track using a road vehicle equipped with flanged wheels for traveling on rails, such as a Hy-Rail vehicle (trademark of Harsco Technologies Corporation). The track survey vehicle is equipped with a differential GPS receiver and a computer, which may be the HEC computer, and track survey software. As the survey vehicle travels along the track, the survey crew, which may be or include a xe2x80x9croadmasterxe2x80x9d, marks spread zones where ballast is to be spread and non-spread zones, such as bridges, road crossings, and the like, where ballast is not to be spread. In some circumstances, it may be necessary for the survey crew to stop the survey vehicle, get out with a portable GPS receiver and computer, and acquire the needed coordinates on-foot. In circumstances where multiple short spread and non-spread zones occur, it may not be possible for the hydraulic actuators to act quickly enough to accurately deposit and inhibit depositing the ballast. In such a case, the entire zone is marked for conventional ballast spreading.
Alternatively, other procedures for determining the spread and non-spread coordinates are foreseen. For example, if a previously obtained track coordinate data file is available, it is foreseen that it could be processed to designate spread and non-spread zones. Further, under some circumstances, track surveying may even conducted on a ballast train, forward of concurrent ballast spreading activity. Under normal circumstances of pre-spread surveying, a track survey data file is created which is transferred to the HEC computer for processing during a ballast spreading run.
In addition to surveying the track for its coordinates to thereby locate zones requiring ballast and those on which ballast is not desirable, it is necessary to survey the ballast train for car identities car order, and car orientation. Each car control unit or CCU includes a designated front communication relay and a designated rear communication relay, both of which are normally closed, that is, normally in a state which maintains communication continuity through the network bus. The relays are individually controllable by the CCU. The CCU is programmed to allow the relays to reclose after a certain timeout if not instructed otherwise. The hopper cars can be assembled into the ballast train in any random order and with some cars oriented front to rear while the rest are oriented rear to front. It is not economically feasible to assemble the ballast train in any particular order or to change the orientation of any particular car. However, the HEC must determine the order and orientation of the cars to enable communication of ballast door commands to the proper car during ballast spreading.
In the present invention, the process of surveying the CCU""s of the hopper cars is referred to as manifesting. In the manifesting process, the HEC queries the CCU""s to report their identities or neuron identification numbers. Then, through an iterative procedure of commanding the cars to open their front and then rear communication relays and report their identities, the HEC is able to determine the order of the cars and their orientations. In particular, after the identities are determined, the HEC broadcasts a command for all cars to open their front relays. Then the HEC calls for any car to identify itself. If the first car in line is forwardly oriented, no car will respond since the front relay being opened, temporarily breaks communication between the HEC and the first car""s CCU. However, if a car identifies itself, the first car must be reversed in orientation since its still closed rear relay maintains communication between the HEC and the first car""s CCU. The car CCU, so identified, is then placed in a no-response mode for the duration of the manifesting procedure. If the first did not respond to the first query with all front relays opened, after a communication relay timeout, all rear relays are commanded to be opened. Now the first car can be identified and determined to be forwardly oriented and is placed in a no-response mode. In a similar manner, the order and orientation of the remaining hopper cars is determined until successive queries with front and rear relays opened fails to receive a response. The data file of identified, ordered, and oriented hopper cars is stored as the manifest data file.
In the present invention, the spreading of ballast is controlled in terms of the amount or weight of ballast spread per unit of track length. Overall, from historic experience and for accounting purposes, the required quantity of ballast is determined in tons per mile. While such a scale is more convenient for determining the cost of the operation, it is too coarse for dynamic control of ballast spreading at a relatively high traveling speed. In the present invention, the track length is divided into xe2x80x9cbucketsxe2x80x9d which are xe2x80x9cfilledxe2x80x9d to achieve an overall desired tons of ballast per mile. The length of th e buckets may be any convenient length and, in the present invention, are set at one foot lengths of track. Since each ballast door can spread either to the inboard side or the outboard side, but not both simultaneously, the track may be divided into an inboard set of buckets and an outboard set, which must be tracked separately. Each bucket has designated coordinates which may include the GPS coordinates of a set of buckets along with a sequential member of such a set. The bucket coordinates are derived by processing a previously generated track survey file.
The spreading process of the present invention tracks the current location of the ballast train reference point in terms of its xe2x80x9cbucketxe2x80x9d location, the current load of ballast in each car, the fill percentage of each bucket, the state of each door as closed or opened and in which direction, and the speed of the train. Because of the lag in response of the ballast door actuators and the movement of the ballast and because of the movement of the train, the spreading process must xe2x80x9clook aheadxe2x80x9d in order to effectively correlate a door state to a given bucket. The spreading process is timer driven and begins executing a series of actions at each timer interval or xe2x80x9ctickxe2x80x9d. In the present invention, the timer interval is at 100 milliseconds or one tenth of a second. Spreading actions are affected by the speed and location of the train and, thus, all calculations factor in the speed and location. In contrast, the flow rate of ballast through a ballast door can generally be considered to be a constant. Preferably, the ballast doors are operated in such a manner as to be considered fully closed or fully open; however, the present invention foresees the capability of operating with the ballast doors in partially open states.
Generally, at each clock tick, the state of each ballast door in succession is checked along with a xe2x80x9clookaheadxe2x80x9d set of buckets and, if the door is currently open, the fill percentage of a current bucket set of buckets which will receive ballast from the door in the current time interval. If the door is closed, the state of the lookahead bucket set is checked to determined if opening the current door will exceed the target fill of those buckets. If not, the current door is opened. If the current door is already open, the fill percentages of the current bucket set are updated, and the lookahead bucket set is checked to determine if the current fill exceeds the target fill. If not, the door stays open.
In general, the threshold to keep a door open is not as strict as the threshold to open a closed door. In zones where spreading is desired, it is preferable to spread somewhat more than the target fill than less. Subsequent maintenance activity involves crews who will properly position the ballast and tamp it into place. Thus, a small excess of ballast is preferable to an inadequate amount. However, in the case of a no-spread zone, any ballast which is deposited may constitute a hazard, such as on a road crossing, and may require a clean-up. For processing purposes, buckets in no-spread zones are initialized as full so that lookahead routines which encounter them always require the current door to close if open or to remain closed.
The spreading process continues until all buckets of a spreading run are filled, all ballast from the hopper cars is exhausted, until the process is interrupted by a detected malfunction in the system, or until the operator shuts the process down for any reason. Generally, ballast is supplied from the forwardmost hopper cars initially, moving rearwardly as the ballast is exhausted from the forward cars. If functions on a hopper car are inoperative, the car is simply bypasses in processing, although it may be necessary to bridge the computer network across such a xe2x80x9cdeadxe2x80x9d car. It is possible that some buckets, particularly near the end of a spreading run, will not be completely filled. Thus, it is desirable to save data representing the final state of any unfilled buckets for a future spreading run. It may also be desirable to save the final state of all buckets and hopper cars for record keeping and accounting purposes.
While the ballast spreading system of the present invention preferably uses location data provided by the GPS system, it is recognized that there are locations in which a GPS receiver will not be able to acquire data from enough satellites to determine position, such as in a tunnel or in some valleys and canyons. The present invention has the capability of supplementing the GPS derived location data with location derived from detecting car wheel rotation. The present invention is adapted to track wheel rotation for a limited distance from the last good GPS data set without significant error.
Although the present invention is described and illustrated principally with reference to spreading ballast on railroads, it is foreseen that the present invention could also find application in other endeavors, such as in agriculture, road building or maintenance, or the like. Thus, the present invention is not intended to be strictly limited to applications in ballast spreading railroad maintenance.
The principal objects of the present invention are: to provide an improved logistics management system and method; to provide such a system and method which utilize differential enhancements of a satellite based global positioning system (GPS), such as the NAVSTAR GPS, for location determination; to provide such a system and method which are adaptable to various types of vehicles and sets of interconnected vehicles; to provide such a system and method which are adapted for use in conjunction with bulk material distributing and spreading operations; to provide such a system and method which are adapted for use with various conventional position determining systems in addition to GPS derived location determination; to provide such a system and method which utilize commercially available GPS equipment; to provide such a system and method which utilize a computer mounted on-board a vehicle with GPS location data input for controlling the distribution of a bulk material along a surface; to provide, particularly, a system and method for spreading ballast along a railroad; to provide such a system employing a plurality of ballast hopper cars, each with a pair of ballast hoppers and associated ballast doors with hydraulic actuators operating the doors to control the flow of ballast from the hoppers; to provide such a system in which each hopper car has a car controller unit (CCU) communicating with a head end controller (HEC) to receive commands to open and close the ballast doors; to provide such a system including a differential GPS receiver positioned on a ballast train including the hopper cars which concurrently detects geographic coordinates of a reference location on the train; to provide such a method which includes surveying a track on which ballast is to be spread using a GPS receiver to collect periodic coordinates of the track and wherein track zones are designated as spread zones or no-spread zones, as appropriate, to generate a track survey data file; to provide such a method including computer controlled querying of the CCU""s of the hopper cars in such a manner as to determine the order and orientation of each hopper car of the train to generate a manifest data file for the particular ballast train; to provide such a method which controls the spreading of ballast on a railroad by dynamically tracking the position of a reference location on the ballast train, the current amount of ballast which already been spread on sections of the track, the remaining ballast load of each hopper car, and the state of each ballast door and, generally, opening a given ballast door or maintaining it open if the ballast spreading therefrom will not exceed a target amount of ballast per unit of track length and closing or maintaining the door closed if the target ballast in a given location would be exceeded; to provide such a system and method which can reduce the time and labor required for a large proportion of ballast maintenance on railroads; to provide such a system of ballast spreading which minimizes the disruption of normal traffic on a railroad; to provide such a system and method which are adaptable for use with various discharge control means in connection with ballast spreading operations; and to provide such systems and methods of ballast spreading which are economical to practice, which are efficient in operation, and which are particularly well adapted for their intended purposes.
Other objects and advantages of this invention will become apparent from the following description taken in relation to the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.
The drawings constitute a part of this specification, include exemplary embodiments of the present invention, and illustrate various objects and features thereof.